Low-methoxyl pectin stabilizes low-fat set yoghurt and improves their physicochemical properties, rheology, microstructure and sensory liking

Abstract

Addition of low-methoxyl pectin (LMP) was observed to reduce whey loss, improve firmness, rheology, quality and overall liking of low-fat set-yoghurt. LMP addition increased soluble solids content and resulted in higher bacterial counts (≥10 log CFU/g), acidity, bioactivity (DPPH• & ABTS+ μM Trolox/g), and lower pH of set yoghurts. A significant (p < 0.05) improvement in firmness and 16% reduction in whey loss was also observed. As per rheology studies, LMP added set yoghurts possessed higher modulus (G′, G″, G*) and complex viscosity. Power law model parameters (A & z) for G* also related to the enhanced strength of yoghurt matrix on addition of LMP. The dense packing of protein gel structure along with filling action of hydrated hydrocolloid might led to moduli changes in yoghurts. Increasing slope of |G*| and dtan δ values close to zero confirmed higher gel strength of yoghurt added with higher concentrations of LMP. Microstructure revealed open porous network of casein in control, while increased cross-linking with casein or filling of cavities was observed upon addition of LMP in yoghurts. Sensory liking scores showed strong correlation with rheological parameters, while PCA confirmed the effect of LMP concentration on major quality attributes.